Femoral Artery Aneurysm

Femoral artery aneurysm is dilatation of the common, superficial or profunda femoral artery to over 1.5 times the normal diameter. The common femoral artery is the usual site. It may thrombose and cause acute limb ischaemia, embolise to the foot, compress the femoral vein or nerve, or rupture.

Isolated true degenerative aneurysm is uncommon. About 90% of patients are men, usually in their 60s and 70s, and about half are bilateral. Most patients have another aneurysm, particularly of the abdominal aorta, iliac arteries or popliteal arteries.

Causes: atherosclerotic degeneration (the main cause of true aneurysm), connective tissue disease, arteritis, infection (mycotic, syphilitic, tuberculous), previous surgery or anastomosis, and trauma. This article covers true aneurysm, with comment on false aneurysm where it changes the approach.

Rupture is rare, but thrombosis and embolisation are common in symptomatic and large aneurysms, and amputation can follow.

Pathophysiology.

Medial degeneration with loss of elastin and smooth muscle, matrix metalloproteinase activity and inflammation weaken the wall. Wall stress rises with diameter.

Mural thrombus lines the sac, and may embolise to the leg arteries, causing blue toe syndrome and distal occlusion, or occlude the aneurysm and the run off vessels, causing acute ischaemia.

The aneurysm lies beneath the inguinal ligament, so hip flexion can kink an endovascular graft and compress it, which affects repair choice.

Pulsatile expansile groin mass, often found incidentally. Symptoms: groin pain, leg swelling from venous compression, thigh numbness or pain from femoral nerve compression, intermittent claudication, rest pain, blue toes, and acute limb ischaemia (pain, pallor, pulselessness, paraesthesia, paralysis). Rupture causes groin haematoma, pain and shock.

• Duplex ultrasound: diameter, thrombus, flow and bilateral assessment, with ankle brachial index and toe pressures.
• CT angiography of the aorta, iliac, femoral and popliteal arteries and run off: extent, neck and landing zones, and associated aneurysms. MR angiography as an alternative.
• Screening for other aneurysms: abdominal aorta and popliteal arteries on both sides (ultrasound).
• Infection workup when suspected (fever, erythema, rapid growth): blood cultures, white cell count, C-reactive protein, and syphilis and tuberculosis tests.
• ECG, creatinine, and cardiovascular risk assessment before surgery.

Differential diagnosis.

• False aneurysm after arterial puncture, graft anastomosis or trauma.
• Femoral hernia, lymph node, abscess, saphenofemoral varix and groin haematoma.
• Soft tissue tumour and iliopsoas bursa.
• Arteriovenous fistula and hip joint effusion.

Medical therapy for all patients.

• Aspirin 75 to 100 mg orally once daily. Atorvastatin 40 to 80 mg daily (LDL cholesterol under 1.4 mmol/L), blood pressure control (under 130/80 mmHg), smoking cessation and glycaemic control.
• Anticoagulation after embolic or thrombotic events (apixaban 5 mg twice daily, 2.5 mg twice daily if two of age 80 or over, weight 60 kg or under, creatinine 133 micromol/L or over; or warfarin to INR 2.0 to 3.0) as determined by the vascular team.

Indications for repair. Symptoms (pain, compression, embolisation, thrombosis, claudication or rest pain), diameter of 2.5 cm or more (some centres use 3.0 cm, or twice the normal artery), rapid growth (over 0.5 cm in a year), mural thrombus, and infection. Aneurysms under 2.5 cm without symptoms or thrombus are observed with duplex every 6 to 12 months.

Acute limb ischaemia from thrombosed aneurysm (emergency).

• Unfractionated heparin 80 units/kg intravenous bolus (usual 5000 units), then 18 units/kg/h, with aPTT 1.5 to 2.5 times control. Analgesia (morphine 2.5 to 5 mg intravenously or fentanyl 25 to 50 microgram).
• Viable or marginally threatened limb with a patent run off: catheter directed thrombolysis with alteplase 0.5 to 1 mg/h (usual total up to about 40 mg) with low dose heparin, then aneurysm repair. Immediately threatened limb: surgical thrombectomy with aneurysm repair or bypass, with fasciotomy for prolonged ischaemia and reperfusion injury.
• Contraindications to thrombolysis: previous intracranial haemorrhage, ischaemic stroke in 6 months, intracranial neoplasm, active bleeding, major surgery or trauma in 3 weeks.
• Monitor potassium, creatinine and creatine kinase for reperfusion injury.

Elective repair.

• Open surgery is the preferred treatment: resection or exclusion of the aneurysm with interposition graft (prosthetic graft, or vein when the artery is small or infection is present), reimplantation or bypass to the profunda femoris artery when the profunda origin is involved, and ligation of side branches. Cefazolin 2 g intravenously within 60 minutes before incision (3 g when weight is over 120 kg); heparin 70 to 100 units/kg intravenously before clamping, reversed with protamine 1 mg for each 100 units given in the previous 2 to 3 hours. Complications are wound infection and lymphocele (about 5 to 15% in groin wounds), bleeding and graft thrombosis. Aneurysm repair has low operative mortality (under 2%).
• Endovascular repair with a covered stent is limited by hip flexion, the need to preserve the profunda, and stent fracture, and is used selectively in high risk patients, with early thrombosis risk.
• Infected aneurysm: draw cultures, vancomycin 25 mg/kg intravenously as a loading dose then 15 to 20 mg/kg every 8 to 12 hours (trough 15 to 20 mg/L) with piperacillin and tazobactam 4.5 g intravenously every 6 hours, adjusted to cultures, with resection and reconstruction using autologous vein or extra-anatomical bypass; at least 6 weeks of antibiotics.

After repair. Aspirin 75 to 100 mg daily lifelong. Warfarin or apixaban only for another indication. Statin and risk factor control. Screen and treat coexisting aortic and popliteal aneurysms.

Monitoring. Duplex at 1 month, 6 months and 12 months after repair, then yearly. Observed aneurysms every 6 to 12 months. Ultrasound of the abdominal aorta and popliteal arteries at diagnosis and as determined by findings. Ankle brachial index yearly.

Referral and escalation. Refer every confirmed aneurysm to a vascular surgeon. Urgent referral for acute limb ischaemia, expanding painful mass, signs of infection, or suspected rupture (same hour, with large bore access and blood).

Special groups.

• Pregnancy: rare; manage with a multidisciplinary team; use aspirin 75 mg and low molecular weight heparin if needed; avoid warfarin and direct oral anticoagulants.
• Older adults and frailty: observe small aneurysms; repair under local or regional anaesthesia where possible.
• Kidney impairment: limit contrast volume and adjust apixaban by creatinine clearance.
• Region specific: mycotic and syphilitic aneurysms and groin sepsis in people who inject drugs are frequent causes of false aneurysm, so test for syphilis, HIV and tuberculosis, and take cultures.